1. Field of the Invention
This invention pertains generally to systems and methods for treating medical conditions associated with the heart, and more particularly to surgical devices and procedures for forming conduction blocks at locations associated with the heart that include cardiac tissue.
2. Description of Related Art
Cellular therapy for treating cardiac conditions has been the topic of significant research and development in recent years, generally for the purpose of increasing cardiac conduction or function. In fact, certain types of injected cells have been observed to couple poorly with indigenous cardiac cell tissues, and various prior disclosures have cited a related decrease in conduction transmission as a significant obstacle to the intended cellular therapy. Some disclosures have cited a desire to in fact modify the properties of injected cells to increase the cardiac tissue coupling for enhanced conduction or contractility.
Tissue engineering techniques utilizing skeletal myoblast transplantation for myocardial repair has in particular gained increased attention with the demonstration that skeletal myoblasts survive and form contractile myofibers in normal and injured myocardium. However, the emphasis of myocardial repair has focused on the preservation of myocardial contractility with little attention given to the effects of tissue engineering on cardiac conduction or effects on cardiac arrhythmias.
In addition, according to previous disclosures skeletal muscle cells may be initially injected as myoblast and thereafter differentiate into myotubes/myofibers. The conduction properties of myoblasts and myotubes are significantly different. Additionally, depending on how old the myoblasts are, they can vary in conduction properties. Therefore, following the injection of certain preparations of myoblasts, a heterogeneous mileau of cells may result which can produce unpredictable insulation results. However, the use of myoblast injections for creation of conduction blocks to treat arrhythmias should nevertheless be effective.
Cardiac arrhythmias are abnormal conditions associated with the various chambers and other structures of the heart, and are typically treated by drug therapy, ablation, defibrillation or pacing. Ablation is generally a treatment technique intended to create conduction blocks to intervene and stop aberrant conduction pathways that otherwise disturb the normal cardiac cycle. Typical ablation technology for forming conduction blocks uses systems and methods designed to kill tissue along the pathway, such as by applying energy to destroy cells via hyperthermia such as with electrical current (e.g. radiofrequency or “RF” current), ultrasound, microwave, or laser energy, or via hypothermia using cryotherapy, or chemical ablation such as destructive ethanol delivery to tissue. Despite the significant benefits and successful treatments that have been observed by creating conduction blocks using various of these techniques, each is associated with certain adverse consequences. For example, ablative hyperthermia or other modes causing necrosis have been observed to result in scarring, thrombosis, collagen shrinkage, and undesired structural damage to deeper tissues.
There is a need for improved systems and methods for treating cardiac arrhythmias.
There is in particular a need for improved systems and methods for forming conduction blocks at locations along cardiac tissue structures without substantially ablating cardiac tissue.